An ICE outboard run for prolonged periods at 5000 RPM will not last long and the fuel consumption at that throttle setting would be horrific. Having said that, electric motors have a pretty flat torque curve which should allow for a prop that takes a bigger bite either through pitch or increased diameter. Most outboard lower units have a horizontal tab above the shaft which limits the diameter of the prop. The following link may be helpful in determining your best prop size. http://www.rundquist.com/how_change_pitch.htm
Good luck,
George
Kevin,
Thanks for responding.
We also concluded, that the weight of these AC induction motors is to high for use in an outboard, hanging from the stern.
We'll probably will go with a brushless Etek/Mars motor, that seems to have more rpm, than the brushed ones.(4000 rpm)
The ICE outboard runs at about 5000 rpm on the plane
We're hoping to compensate for the "lacking" 1000 rpm or so, by fooling with higher pitched /diameter props and different outboard legs.
Does anybody have an opinion on the feasibility of this?
Rob on Linda
--- On Thu, 5/19/11, Kevin Pemberton <pembertonkevin@gmail.com> wrote:
From: Kevin Pemberton <pembertonkevin@gmail.com>
Subject: Re: [Electric Boats] Electric planing dinghy
To: electricboats@yahoogroups.com
Date: Thursday, May 19, 2011, 6:26 PMI guess you are asking about AC induction motors sold by EV companies.
Induction motors cover a much broader spectrum.
The industrial controllers used on 3ph motors can run the RPMs up to
double or more the rated RPM of the motor. According to literature on
the net 1800RPM motors when used with VFDs are the most efficient. The
controller I use with my 1800RPM motor will give 2.5 times the design
speed of the motor. The torque flat lines at 1800RPM, but this should
not be a problem as the motor still gives 100% of the torque it was
designed to give. DC motors give RPM based on voltage, induction motors
give the RPM based on frequency of the drive. You will not be able to
get more HP from the motor because of the controller design, limits
current, based on the motor connected to it, so size the motor
correctly. AC induction motors are larger and heavier than the DC motors
of the same HP. Inside a boat no problem, off the transom? Maybe.
You could use industrial equipment for your job, but high voltage (over
48) requires much more attention to legal issues. I invision supply
inverter(24 to 220), VFD, and motor under the hood of the outboard. 24v
supply cables into the hood completely water proof. Cooled using water
and coils around the motor and water heat sinks on the VFD and inverter
housing.
Seems like a lot of work!
Kevin Pemberton
On 05/16/2011 03:49 PM, rob linda wrote:
> We're still trying to make up our mind about the rpm issue, one
> encounters, if replacing the ICE power head on the outb
> oard with an electric motor for planing speed.
> Miles suggested belt gearing, which means extra bearing at high end of
> drive shaft.
> There also may be props pitched high enough, if we can find them.
> There is the Agni motor, which is pricey and probably overpowered.
> We're focussing at the moment on using an AC induction motor like
> this: http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac9.php
> At 6000 rpm this seems like a candidate.
> Looking at the power/rev curve :
> http://www.electricmotorsport.com/store/pdf-downloads/AC_Drives/AC9.pdf
> , it has this "bump" at 2000 rpm and looks like the power curve for a
> planing dinghy, where the "bump" happens while "getting on the plane",
> or am I guilty of naive and wishful thinking.
> Any opinions on this ?
> Anybody has experience with AC induction motors?
> Thank you
>
> Rob on Linda
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